Harnessing the power of cavitation to improve production and profit margins | Modern Mining June 2021 Article
The following article was published in the June 2021 edition of Modern Mining Magazine. Check it out here.
As mining companies seek to improve production yields and profitability of marginal operations, it is time to shift mindsets and challenge the conventional processes in the metallurgical industry. With GoldOre’s MACH REACTOR – a game-changing technology that harnesses the power of cavitation – mining operations can extract minerals in the most efficient way possible, thus achieving or even surpassing production targets and improving profit margins. – By Munesu Shoko.
As mining-company leaders work to rebuild profitability, improving productivity is high on the agenda.
Doing more with less is the foundation of improving performance in mining and leads directly to increased shareholder returns. For mining operations pursuing productivity-enhancing approaches and improving yields, GoldOre (Pty) Ltd’s disruptive technology, the MACH REACTOR, is exactly what the industry needs to improve production yields and profitability of marginal operations.
Adrian Singh, founder of GoldOre and the inventor of the MACH REACTOR, explains that the MACH REACTOR is a game-changing technology that harnesses the power of cavitation, permitting certain chemical reactions that would otherwise not be possible. In fact, he says, it is the only high shear/cavitating device currently on the market that is completely self-aspirating, allowing it to be operated without pressurised gas supply. The self aspirating aspect, combined with the comparatively lower power draw makes it particularly suitable to projects where power costs are high, or where power is self-generated.
Commenting on how the technology came into being, Singh says that, having been in the mining industry since 1989, with a wealth of experience in production, research, laboratory techniques, plant design, and technology development, he felt it was time to put together the various bits and pieces of ideas he had gathered over the years. Exactly on Christmas day in 2010, the concept of the MACH REACTOR was born. As Christmas is generally a time of feasting, the idea was scribbled on a paper serviette, and the rest is history. The MACH REACTOR went on to be granted patent rights in just about every country in the world.
What is the MACH?
The MACH REACTOR, explains Singh, is a hyper shear mass transfer reactor that harnesses the exceptional power of controlled cavitation to generate pico-bubbles to greatly enhance the mass transfer of gas into solution and create a highly charged environment promoting chemical reactions that would otherwise traditionally not be possible.
“In the flotation application, these pico-bubbles nucleate on the very minerals that we would like to float and so create a situation where particles ‘give birth’ to bubbles and thus facilitate the flotation of valuable fines, in particular, those that are traditionally lost to tailings owing to their very poor probability of making contact with a flotation sized bubble. The flotation of fully liberated fine mineral leads to a kind of flotation euphoria where higher concentrate grades as well as recoveries are possible at reduced mass pulls, a feet hitherto unachievable without the MACH,” he says.
In the leaching application, the pico-bubbles act as a vehicle to finely disseminate and dissolve gases required for leaching while removing passivating layers, reducing boundary layer thickness and improving diffusion and hence mass transfer. The benefits of higher recoveries, faster kinetics and reduced reagent consumptions combine to reduce Capex and Opex and improve project IRR and NPV values.
The technology therefore aids in the extraction of minerals in the most efficient way possible, helping mines achieve and surpass production targets and improve their profit margins. It can be deployed across applications, including platinum group metals (PGMs), gold, base metals, as well as for environmental applications such as cyanide destruction and acid mine drainage – “the possibilities are endless and the market is global,” says Singh.
“The MACH is a cavitational reactor which generates very fine pico-bubbles. This is useful in extracting very fine minerals which are traditionally lost to flotation circuits,” he says. “Because of the fine bubble generation formed inside the MACH REACTOR, the technology is able to collect the fine minerals, improving flotation in a way that, up until now, has never been done anywhere in the world.”
Understanding hydrodynamic cavitation
Cavitation is not something that is usually applied within the metallurgical industry, but in the MACH REACTOR, GoldOre has found a way to harness the powerful energy to give the industry a revolutionary piece of technology.
The technology is completely different from the traditionally and widely known offerings that employ the principles of mixing and shear. Explaining the difference, Singh says conventional shear technology is based on mixing and shear, which is the interaction of one layer of fluid upon another. “Increasing mixing intensity improves efficiencies and takes the system towards shear conditions,” he says.
However, beyond shear lies the concept of cavitation. It has traditionally been regarded as a negative concept in the engineering field for many years, says Singh. “If you speak to any engineer about cavitation, they will throw their hands up in the air in despair because cavitation has been proven to damage pumps and cause excessive wear in pipelines,” he explains.
“Engineers are taught to design in a way that avoids cavitation by all means possible. I had to turn my mind inside out, to say if I could control ‘this animal’ called cavitation, what benefits could I potentially get? The energy release due to the temperature inside one cavitating bubble is up to 5 500°C, and the pressure of the jet that splits that bubble is 1 000 atmospheres. Why would I settle for mixing if I could get that?”
Singh went on to design a hydrodynamic cavitation device, which is what the MACH is, using a system of venturis. The speeds of liquids and gasses are exceptionally high and approach the speed of sound, hence the name ‘MACH’ – the way engineers describe speed. Hydrodynamic cavitation is the process of accelerating a liquid through a constriction such as a venturi until the instantaneous pressure drops to below water vapour pressure and causes tiny cavities to nucleate on hydrophobic particles in the liquid. This process is otherwise known as ‘cold boiling’.
The cavities may be ventilated with a gas to be dissolved and are finely disseminated when the cavities collapse in higher pressure regions and form pico-, nano-, and micro-bubbles with a tremendous energy release. This energy is used positively within the MACH REACTOR to clean particle surfaces, break particles for better liberation, emulsify reagents and dissolve gas. “The imploding cavitating bubbles in the venturis of the MACH reactor constitute the ‘heart of the technology. These imploding bubbles generate extreme temperatures of up to 5 500°C and pressures of around 1 000 atmospheres. This creates a highly reactive environment for mass transfer and chemical reaction, allowing certain reactions to take place that would otherwise not be possible. The MACH REACTOR uses this power of cavitation to drastically improve metallurgical processes,” explains Singh.
A key benefit of this technology is its durability. Having been involved with the so-called predecessor technologies of the MACH, Singh says whereas, in the past, new shear reactor technologies gave some interesting benefits, their downside was always the lack of durability – the technology just didn’t last. In fact, in abrasive applications, shear reactors had to be replaced almost every month! The cost of replacing this technology on a regular basis is just out of the question for mines. “You can imagine that this piece of equipment weighs in at about a tonne, and you need cranes, riggers, and fitters every time you replace it. The mining industry doesn’t appreciate such downtime at operations,” says Singh.
The MACH REACTOR scores with its ruggedness. To provide context, GoldOre’s first installation was seven years ago, but that unit is still going strong and there is no replacement required anytime soon. Some of the units have been operating in harsh conditions in Russia and Kazakhstan, for example, but have not been replaced since installation.
Additionally, no wear parts have been replaced. In fact, the technology is designed to match project life. “The MACH REACTOR is a plug-and-play unit, you put it in, and off you go. With no moving parts, it doesn’t need any maintenance, which translates into huge cost savings for mines,” he says.
Higher recoveries are almost always guaranteed with the MACH REACTOR. “At the end of the day, gold mines, and mining operations in general, are there to show a profit to shareholders. While they may not necessarily understand anything about pico-bubbles or cavitation, one thing every business person understands is profit, and that’s where we make a difference with the MACH – it goes directly to the bottom line. We improve recoveries, translating into extra ounces. Extra ounces mean more revenue and ultimately better profits,” says Singh.
While the benefits of this technology have been proven and are there for all to see, Singh says the mining sector has generally been sceptical of trying new ways of working. At the end of the day, the majority of customers that have opted for the MACH REACTOR were companies that “had their backs against the wall”.
For example, the MACH REACTOR literally kept a company that was retreating PGM tailings in business. Having had no success with a variety of technologies, this company was on the verge of closure. “They basically told me the first day we met that they had tried everything else and nothing worked. If the MACH didn’t work, they would have to close shop,” he says.
“We did extensive test work in the laboratory and eventually installed the MACH REACTOR throughout the plant and the company is still in business today,” adds Singh.
Elsewhere, the MACH REACTOR came to the rescue of a Ghanaian gold company that needed capital to build extra leach tanks. The company didn’t necessarily have the money to put in the required extra leach tanks. “We retrofitted the MACH onto their existing plant some four years ago. The faster leach kinetics provided by the technology not only obviated the need for extra leach tanks but also provided a recovery benefit to boot. To this day, they have not installed any additional leach tanks,” says Singh.
In conclusion, Singh says, with this ‘Proudly South African’ product, GoldOre is only scratching the surface of what is possible. What’s stopping its quick uptake is not the application or ability to prove what it can do, but the mindset in the industry.
“People are referring back to what they knew in the year 2000 and are drawing comparisons with something that they haven’t tried yet. Technology has moved on. I always say that the MACH REACTOR is the ‘Tesla’ of the mining industry. It is at the fore front of the metallurgical revolution,” concludes Singh
- The MACH REACTOR is a game-changing technology that harnesses the power of cavitation, permitting certain chemical reactions that would otherwise not be possible
- The MACH REACTOR is the only high shear/cavitating device currently on the market that is completely self-aspirating, allowing it to be operated without pressurised gas supply
- The self-aspirating aspect, combined with the comparatively lower power draw, makes it particularly suitable for projects where power costs are high, or where power is self-generated
- The technology can be deployed across applications, including PGMs, gold, base metals, as well as for environmental applications such as cyanide destruction and acid mine drainage